1. Field of the Invention
The present invention relates to a process of polymerization, catalyst therefor, to products made therefrom, and to hydrogenation. In another aspect, the present invention relates to method of olefin polymerization, to a hydrogenation/olefin polymerization catalyst therefor, and to products made therefrom. In even another aspect, the present invention relates to a method of olefin polymerization utilizing hydrogen pulsing, to a hydrogenation/olefin polymerization catalyst therefor, and to broad molecular weight distribution products made therefrom. In still another aspect, the present invention relates to a method of propylene polymerization, to a hydrogenation/olefin polymerization catalyst therefor, and to broad molecular weight distribution polypropylene made therefrom.
2. Description of the Related Art
In the production of polyolefins, it is desirable to have some control over the molecular weight distribution of the produced polyolefin.
U.S. Pat. No. 4,914,253, issued Apr. 3, 1990 to Chang, discloses a process for preparing polyethylene wax having a narrow molecular weight distribution in a gas phase polymerization reactor. The catalyst is derived from the addition of silica gel containing about 6 to 20 weight percent adsorbed water to a trialkylaluminum solution. An alumoxane coated silica gel is formed to which a metallocene is added and formed into a free flowing powder. Chang further teaches that a direct correlation exists between the molecular weight of the polymeric wax obtained and the amount of hydrogen utilized during polymerization. Control of the molecular weight is achieved by varying the amount of hydrogen utilized and the reaction temperature. The catalyst test example discloses that during polymerization, ethylene, hydrogen and nitrogen were continuously fed to the reactor.
U.S. Pat. No. 4,935,474, issued Jun. 19, 1990 to Ewen et al., discloses a process and catalyst for producing polyethylene having a broad molecular weight distribution. The polyethylenes are obtained directly from a single polymerization process using a catalyst system comprising at least two different metallocenes each having different propagation and termination rate constants, and an alumoxane.
U.S. Pat. No. 4,975,403, issued Dec. 4, 1990 to Ewen, discloses a catalyst system for producing polyolefins having a broad molecular weight distribution. The catalyst system includes at least two different chiral, stereo-rigid metallocene catalysts of the formula R"(C.sub.5 (R').sub.4).sub.2 MeQ.sub.p and an aluminum compound.
U.S. Pat. No. 5,124,418, issued Jun. 23, 1992 to Welborn, Jr. discloses a catalyst and process having the capability of producing polymers having a varied range of molecular weight distributions, i.e., from narrow molecular weight distribution to broad molecular weight distribution and/or multi-modal molecular weight distribution. Broad molecular weight polyethylenes can be obtained by employing on one support metallocenes and transition metal components which will have different propagation and termination rate constants for ethylene polymerization. The molecular weight distribution of the polyethylenes can also readily be controlled by varying the molar ratios of the metallocene to transition metal component on the support. Further discloses that conventional polymerization adjuvants such as hydrogen, can be employed to control the molecular weight of the polyethylene produced.
U.S. Pat. No. 5,359,015, issued Oct. 25, 1994 to Jejelowo, and U.S. Pat. No. 5,281,679, issued Jan. 25, 1994 to Jejelowo et al., disclose a metallocene catalyst system and process of producing polyolefins having a controllable broadened molecular weight distribution. The cyclopentadienyl ring comprises as a molecular weight distribution broadening substituent, a hydrocarbon group having from 3 to 20 carbon atoms, with one of the carbon atoms being a 2.degree. or 3.degree. carbon which is covalently bonded to the cyclopentadienyl ring. Control of the molecular weight distribution is provided by varying the types of substituents on the ring. The process may utilize conventional polymerization adjuvants, such as hydrogen.
U.S. Pat. No. 5,382,631, issued Jan. 17, 1995 to Stehling et al., discloses linear ethylene interpolymer blends of interpolymers having narrow molecular weight and composition distributions. Discloses that in slurry polymerization, a suspension of solid, particulate polymer is formed in a liquid polymerization medium to which ethylene and comonomers and often hydrogen along with catalyst are added. Further discloses that in gas-phase polymerization, performed in a stirred or fluidized bed of catalyst and product particles, that thermostated ethylene, comonomer, hydrogen and an inert diluent gas such as nitrogen can be introduced or recirculated so as to maintain the particles within a temperature range.
U.S. Pat. No. 5,420,217, issued May 30, 1995 to Canich, discloses a polyolefin polymerization process using a Group IV B transition metal component and an alumoxane component to polymerize propylene to produce amorphous polypropylene.
However, in spite of these advancements in the prior art, none of these prior art references disclose or suggest polyolefin polymerization utilizing hydrogen pulsing, nor the use of a metallocene catalyst as a hydrogenation component.
Thus, there is still a need for an improved polyolefin polymerization process.
There is another need in the art for improved polyolefin process catalysts.
There is even another need in the art for improved polyolefin products.
These and other needs in the art will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.